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Abstract

"Streambank erosion of the Osage River downstream of Bagnell Dam is naturally-occurring; however, it may be significantly worsened due to releases made from the dam to generate hydropower. In this study, six typical outflow release patterns from Bagnell Dam were evaluated to determine their effects, if any, on the stability and the rate and amount of erosion of the banks of the Osage River.

The Bank Stability and Toe Erosion Model (BSTEM), version 5.2, was used to carry out the erosion and stability calculations. The model was validated by using data from another study and comparing the results from BSTEM with those of the other study. BSTEM produced very similar results, and it was thus concluded that it would provide a reliable analysis for this study. The six outflow scenarios were evaluated, and those that resulted in the greatest amount of erosion and bank instability were identified based on the model results.

A sensitivity analysis was also completed to determine the input data necessary to BSTEM that would have the greatest impact on the model outcome. The input parameters evaluated in the sensitivity analysis included various geotechnical properties, assumptions regarding depth to the phreatic surface, and the timing and slope of the outflow hydrographs.

The results of this study indicate that the streambanks of the Osage River are quite stable when erosion of the noncohesive toe material is not considered; however, when erosion is accounted for, most of the banks become unstable during the outflow scenarios. Based on the typical bank stratigraphy, the most common failure mechanism that would be encountered on the Osage River is mass wasting or cantilever failures"--Abstract, page iii.